47 research outputs found
Forms of Glacial Relief of Spitsbergen Glaciers
No full textResults are given of radio echo‐sounding of 53 glaciers of different sizes and glaciological regimes during 1974–75 and 1977–79 in Spitsbergen. Mountain glaciers have maximum ice thicknesses ranging from 90 to 350 m. Thicknesses up to 165 m, as well as the presence of overdeepened sections of the bed and subglacial ridges up to 100 m high are typical. Other glaciers have ice thickness values of up to 500 m (e.g. Veteranen) but on some sections of glaciers and ice caps depressions in the bed with ice thicknesses reaching 540 m have been found, which exceed the “background” thickness by 200 to 400 m. Subglacial relief of Vestfonna, Nordaustlandet, is very rough in its outer region but is rather smooth in the central part beneath the ice dome, where ice thickness reaches 385 m. Multiple correlation analysis of 15 glaciers indicates a number of significant relationships between the area of terminal and lateral moraines of glaciers and length, area, and, consequently, volume.</jats:p
Radio Echo-Sounding of Sub-Polar Glaciers in Svalbard: Some Problems and Results of Soviet Studies
No full textThe paper discusses data analysed from airborne radio echo-sounding of Svalbard glaciers at frequencies of 440 and 620 MHz. Bottom returns from depths greater than 200 m are recorded with fewer gaps if the more powerful 620 MHz radar is used, and if measurements are carried out in the spring before intensive melt on glaciers. For all relatively thin glaciers and some glaciers up to 320–625 in thick, the track with bed returns is still rather common, apparently caused by their colder temperature regime. However, because of severe scattering of radio waves, this procedure still does not solve the problems of the echo-sounding of accumulation areas of many of the larger glaciers, the ice plateau, and heavily crevassed parts of glaciers.For considerable areas of those Spitsbergen glaciers which have a thickness greater than 200 m, internal radar reflections (IRR) were registered as a single isolated layer from depths usually ranging from ¼ to ½ of their thickness. Studies of two deep bore holes on Fridtjovbreen have- demonstrated that such IRR are related to a boundary between cold ice and water-bearing ice near the melting point. These IRR can be interpreted as indicators of a special class of two-layered or transitional glacier, and of the location within them of the ice-melt isotherm.</jats:p
Radio Echo-Sounding of Sub-Polar Glaciers in Svalbard: Some Problems and Results of Soviet Studies
No full textThe paper discusses data analysed from airborne radio echo-sounding of Svalbard glaciers at frequencies of 440 and 620 MHz. Bottom returns from depths greater than 200 m are recorded with fewer gaps if the more powerful 620 MHz radar is used, and if measurements are carried out in the spring before intensive melt on glaciers. For all relatively thin glaciers and some glaciers up to 320–625 in thick, the track with bed returns is still rather common, apparently caused by their colder temperature regime. However, because of severe scattering of radio waves, this procedure still does not solve the problems of the echo-sounding of accumulation areas of many of the larger glaciers, the ice plateau, and heavily crevassed parts of glaciers.
For considerable areas of those Spitsbergen glaciers which have a thickness greater than 200 m, internal radar reflections (IRR) were registered as a single isolated layer from depths usually ranging from ¼ to ½ of their thickness. Studies of two deep bore holes on Fridtjovbreen have- demonstrated that such IRR are related to a boundary between cold ice and water-bearing ice near the melting point. These IRR can be interpreted as indicators of a special class of two-layered or transitional glacier, and of the location within them of the ice-melt isotherm.</jats:p
Interpretation of Radio-Echo Sounding Data on a Temperate Mountain Glacier from its Surface
No full textTemperate mountain glaciers have specific peculiarities which make the interpretation of radio-echo sounding data much more difficult than for polar ice sheets. On the A or Z indicators one can observe a plurality of pulses differing in shape, amplitude, and range. Often a gap is observed on the film. The problem is to select the pulses from the bed or internal reflecting horizon and to reconstruct the subglacial relief or internal interface.During preliminary processing, the radio-coordinates of all marks on a type A radiogram are written into a table. Then non-informative marks are eliminated and informative marks are situated on a continuous line or trace.We put into practice three methods of interpretation: (1) an envelope method, (2) Harrison’s transformation method, (3) approximation of segments of a trace by straight lines. Harrison’s transformation method is the most general one; the others are useful for the presentation of results in a graphical form. The suggested methods are used for the interpretation of the data from a transverse profile of the valley glacier Lednik Bezengiy, Caucasus, 1970-71. Radar RW-10 with a carrier frequency of 440 MHz and overall receiver sensitivity relative to the transmitter pulse power 130 dB was used. It was revealed that the transparency of the glacier changes from year to year. The maximum ice thickness measured was 33°±15 m. Some extended interfaces in the body of the glacier were discovered. One of them, 80 m deep, coincides with seismic contrast interface and with the 0° C isotherm. Radio-echo sounding data are in agreement with gravity measurements on the same profile.</jats:p
Fifty years of geophysical researches of glaciers in Institute of Geography, the Russian Academy of Sciences, 1966–2016
Get PDFIn 1967‑2015, Institute of Geography of the USSR/Russian Academy of Sciences together with other organizations carried out field expeditions in different areas of mountain and polar glaciations in many regions: the Polar Urals, Caucasus, Pamir, Zailiysky and Jungar Alatau, Tien‑Shan, Pamir‑Alai, the Kamchatka Peninsula, the Pyrenees, the Arctic – Spitsbergen, Novaya Zemlya, Franz Josef and Severnaya Zemlya, and Antarctica – on the ice flow B, and in the sub‑Antarctic – Islands King George, Galindez, and Livingston. The gravimetric and ground and aerial radar observations were made in these expeditions. About 300 glaciers of different morphological types and sizes with cold, subpolar and temperate thermal regime were studied. Basic results of these studies are the following: (1) the new data on the ice thicknesses, ice volumes, subglacial relief, internal structure, and thermal state of the glaciers were obtained; (2) the two‑layered (polythermal) glaciers consisting of the upper layer of cold ice and the lower layer of temperate water‑filled ice had been revealed in Svalbard for the first time; spatial distribution of cold, polythermal and temperate glaciers had been determined; (3) the evidences were obtained that measured changes in thickness of the upper cold ice layer in polythermal glaciers can be used to estimate the long‑period variations of regional climates and serve as regional paleothermometers; (4) methods for estimating the water content in temperate and polythermal glaciers from the RES data were developed; and its space‑time variations in temperate ices of the Svaldbald glaciers were estimated since even small water content inside of them can noticeably change their dynamic behavior; (5) methods for estimating the ice volume within glaciers in large regions of mountain and polar glaciations had been created; the ice storages were estimated in Svalbard, Franz Josef Land, Dzhungrsky Alatau, the Great Caucasus, and Mt. Elbrus; (6) detailed data on the ice thicknesses and the subglacial relief had been obtained for 40 glaciers in framework of different national and international programs and projects; the data can be used to solve a wide range of practical and theoretical problems, including numerical modeling. These studies demonstrated the following: (1) the use of monopulse radars VIRL‑6 and VIRL‑7 of decameter range (the central frequency is 20 MHz) with digital recording of the radar and GPS data is quite efficient for ground‑based and airborne (from helicopters) radio‑echo sounding of mountain and polar glaciers with their ice thicknesses up to 500–600 m; (2) it was found that thicknesses of glaciers in the Caucasus and Tien Shan can reach 330–430 m, while in regions of mountain, ice‑sheet and transitional glaciation on the Spitsbergen Archipelago – 300, 560 and 600 m, respectively, on the ice caps of the Franz‑Josef Land and Severnaya Zemlya – 450 and 813 m, and on King George and Livingston Islands (Sub‑Antarctica) – 330 and 500 m; (3) large parts of ice caps and outlet glaciers in Svalbard, Franz Josef Land, Severnaya Zemlya which beds were located below the sea level were found. Precisely these parts can be undergone quick shortening due to climate warming, and, thus, cause formation of icebergs making threats for ships and gas‑oil marine platforms in the Barents and Kara seas; (4) data of the measurements made possible to calculate volumes of a number of investigated glaciers and ice caps and to estimate the ice storages in large areas of mountain and polar glaciations (the Jungar Alatau, Great Caucasus, Spitsbergen, Franz Josef Land); (5) decreasing of glacier volumes on the Franz Josef Land and some Spitsbergen glaciers for the last decades had been estimated. Analysis of the data obtained had shown that considerable part of polythermal glaciers in Spitsbergen belong to type of surging glaciers; they have the winter englacial runoff and form the near‑glacier icings. It allows considering such glaciers as dynamically unstable, predisposed to surges as well as possible sources of winter water supply and additional sources of paleoinformation about long‑period variations of regional climate
Interpretation of Radio-Echo Sounding Data on a Temperate Mountain Glacier from its Surface
No full textTemperate mountain glaciers have specific peculiarities which make the interpretation of radio-echo sounding data much more difficult than for polar ice sheets. On the A or Z indicators one can observe a plurality of pulses differing in shape, amplitude, and range. Often a gap is observed on the film. The problem is to select the pulses from the bed or internal reflecting horizon and to reconstruct the subglacial relief or internal interface.
During preliminary processing, the radio-coordinates of all marks on a type A radiogram are written into a table. Then non-informative marks are eliminated and informative marks are situated on a continuous line or trace.
We put into practice three methods of interpretation: (1) an envelope method, (2) Harrison’s transformation method, (3) approximation of segments of a trace by straight lines. Harrison’s transformation method is the most general one; the others are useful for the presentation of results in a graphical form. The suggested methods are used for the interpretation of the data from a transverse profile of the valley glacier Lednik Bezengiy, Caucasus, 1970-71. Radar RW-10 with a carrier frequency of 440 MHz and overall receiver sensitivity relative to the transmitter pulse power 130 dB was used. It was revealed that the transparency of the glacier changes from year to year. The maximum ice thickness measured was 33°±15 m. Some extended interfaces in the body of the glacier were discovered. One of them, 80 m deep, coincides with seismic contrast interface and with the 0° C isotherm. Radio-echo sounding data are in agreement with gravity measurements on the same profile.</jats:p
Radio Echo-Sounding of Svalbard Glaciers
No full textAbstractPeculiarities of radio echo-sounding of mountain glaciers and ice fields between nunataks from terrestrial vehicles and from helicopters are considered in this paper. The possibility of using comparatively high frequencies (of up to 865 MHz) for sounding such glaciers is demonstrated on the basis of experimental data. Results of airborne radio echo-sounding of Svalbard glaciers of various types, dimensions, and regime obtained with the help of the 620 MHz airborne equipment of high resolution are shown. Returns from the glacier bed have been obtained on the majority of glaciers under investigation. The firn regions of ice fields with temperate regimes flowing between nunataks are, mostly, an exception. Depression in the glacier bed with the ice thickness up to 540 m, as well as internal reflecting boundaries have been detected in some glaciers. Ice volumes of glaciers have been determined from the airborne radio echo-sounding data with the use of a parabolic approximation to the cross-section glacier profiles. Good correlational dependence between ice volume and surface area of glaciers has been established and is used to estimate the ice and water resources in Svalbard glaciers.</jats:p
Radio Echo-Sounding of Svalbard Glaciers
No full textAbstractPeculiarities of radio echo-sounding of mountain glaciers and ice fields between nunataks from terrestrial vehicles and from helicopters are considered in this paper. The possibility of using comparatively high frequencies (of up to 865 MHz) for sounding such glaciers is demonstrated on the basis of experimental data. Results of airborne radio echo-sounding of Svalbard glaciers of various types, dimensions, and regime obtained with the help of the 620 MHz airborne equipment of high resolution are shown. Returns from the glacier bed have been obtained on the majority of glaciers under investigation. The firn regions of ice fields with temperate regimes flowing between nunataks are, mostly, an exception. Depression in the glacier bed with the ice thickness up to 540 m, as well as internal reflecting boundaries have been detected in some glaciers. Ice volumes of glaciers have been determined from the airborne radio echo-sounding data with the use of a parabolic approximation to the cross-section glacier profiles. Good correlational dependence between ice volume and surface area of glaciers has been established and is used to estimate the ice and water resources in Svalbard glaciers.</jats:p
Velocity of radio waves in glaciers as an indicator of their hydrothermal state, structure and regime
No full textAbstractThe results of measurements of radio-wave velocities (RWV) by wide-angle reflection (WAR) methods in the temperate Abramov Glacier in the Alai Mountain Ridge and the “two-layered” sub-polar Fridtjovbreen and Hansbreen on Svalbard using a low-frequency (2–13 MHz) radar are considered and discussed. The experimental data obtained and the data from the literature show that the values of RWV could be a good indicator of the hydrothermal state of glaciers. As such, these data enable the identification of cold, temperate and transitional (two-layered) glaciers, and can be used for estimation of the water content in glaciers and changes in the hydrothermal state.</jats:p
